In order to prevent a switching element from being broken down due to an over-current and prevent circuit parts other than the power element from being broken down due to a current above a permissible current value in a system equipped with a power switching element, the system is required to be provided with a function for monitoring a current value flowing into the power switching element and restricting the current.
As means of providing the current detection function as described above in an insulated gate bipolar transistor (IGBT) element has been proposed as disclosed in Japanese Laid-open Patent Application No. 60-94772 or Japanese Laid-Open Patent Application No. 2-138773, for example. However, in the former, a resistor for obtaining a current detection signal is required to be set up at the outside thereof, and thus it has a problem that an assembly cost is increased and the size of an assembly is increased. In addition, there is a problem that a part of an element current is sacrificed because the current is partially diverted. On the other hand, the latter proposes such a construction that no resistor is required to be set up at the outside, however, in this construction a signal detection electrode is provided in the neighborhood of a channel portion of a cell area, so that a p-base area of this construction is required to be longer in lateral direction than a usual length to set up a contact area. Therefore, there is a problem that latch-up current value is depressed due to an increase of holes flowing into the p-base area.
This invention has been implemented in view of the above various problems, and has an object to provide an IGBT equipped with a current detection structure which requires no signal detecting resistor at the outside thereof, and induces no depression of latch-up current value.